1. Field of the Invention
This invention relates generally to planetary gear type automotive transmissions and, more particularly, to a planetary gear set and method of assembling the same in an automated operation.
2. Description of the Prior Art
In assembling planetary gear type automotive transmissions, it is common practice to mount the transmission case on a fixture which permits end-for-end inversion of the case so that internal components can be installed from opposite ends of the case. It is also common to install a planetary gear set in a sequence which includes installation of the sun gear and ring gear of the set on the case before the planet gears and planet carrier of the set. As an element of this last mentioned step, the planet gears, which are already mounted on the carrier and independently rotatable relative to each other, are usually "timed" on either the sun gear or the ring gear. Timed, as the term is used herein, means meshing engagement of all of the planet gears with one of the sun and ring gear (hereinafter the "timing gear") before engagement of any of the planet gears with the other of the sun and ring gears. After the planet gears are timed on the timing gear, they easily mesh with the other of the sun and ring gear because the planet gears then rotate in unison. A robot for automatically performing this last step can be programmed to advance the carrier along a fixed axis and to rotate it about that axis but may require expensive machine vision technology because the necessary precise alignment of the planet carrier on the axis of rotation of the timing gear may not be easily achieved due to manufacturing tolerances in the components of the transmission and the end-for-end inversions of the case. Where the ring gear is part of a disc clutch assembly, as is common, the assembly procedure is even more difficult because the ring gear may bear a markedly eccentric relationship to the sun gear. The planetary gear set and assembly method according to this invention enables the planet carrier assembly operation to be performed by a robot, without machine vision technology, programmed only to advance the carrier along an axis and to rotate the carrier about that axis.